Analyses for Urban Biodiversity
Any city can evaluate existing conditions for each of the seven elements of urban biodiversity. Since the list of potential analyses is endless, cities can focus their approach by:
- Identifying high-quality datasets that are available and easily accessible,
- Assessing available staff resources and technical capacity,
- Soliciting input from partners and stakeholders, and
- Selecting key questions that will inform planning and resource management.
Click on each element below to learn more about how you can analyze the seven elements of urban biodiversity in your city
Patch Size
Total park area at the city scale summarizes the amount of green space that can support ecosystem health, wildlife, and/or recreational activities. Total park area at the neighborhood scale can help identify where more green space is particularly needed. In areas with very few parks, acquiring new park land might be an important priority. Further analyses and community engagement can help refine open space planning.
Types of Data Used in This Analysis:
- Protected Areas
Analyzing the distance between patches summarizes how far animals or people would have to travel to get from one patch to another. It is important for identifying patches that are particularly isolated and limited in their ability to benefit biodiversity at a landscape scale. Improving connectivity between these patches and creating new intermediate patches can better enable these existing patches to support ecosystem health and functioning.
Types of Data Used in This Analysis:
- Protected Areas
This analysis identifies undeveloped open space near existing parks. This step is critical for identifying opportunities that would expand existing habitat patches. Large, contiguous habitat patches can support a wider diversity and abundance of wildlife than smaller, disconnected patches, creating a biodiversity hub within an urban landscape.
Types of Data Used in This Analysis:
- Protected Areas
- Land Cover / Land Use
- Parcel Data
This analysis uses land cover data to differenitate between high and low quality habitat within natural areas and parks. A soccer field with mowed grasses or turf provides far less biodiversity benefits than a forest patch with understory vegetation, yet both cover types could be within park lands. Determining the proportion of park land that provides high-value habitat is critical for understanding the on-the-ground quantity and quality of habitat in the city. This analysis could also be used to identify protected parks with low-quality habitat, or highlight regions within the city that particularly lack high-quality natural areas, which can help identify important candiate projects for turf replacement or restoration.
Types of Data Used in This Analysis:
- Protected Areas
- Land Cover / Land Use
The patch shape index (or core-to-edge ratio) compares a patch’s total area to the length of its edge, or perimeter. Square or circular patches have more core habitat and shorter perimeters, and are thus more suitable to area-sensitive species than long, skinny patches of similar size. Calculating the shape index of all patches within a landscape can identify patches that are likely to support urban-sensitive species, as well as highlight patches that would benefit from creating adjacent patches to improve the core-to-edge ratio.
Types of Data Used in This Analysis:
- Protected Areas
- Parcel Data
Connections
Corridors are linear open spaces with continuous canopy or vegetation cover that connect patches and help animals move through the landscape. Wider corridors provide more protection from urban stressors and may support movement of a greater variety of species, including forest-interior birds, large mammals, and other potentially urban-sensitive wildlife. Along a stream or river, wider corridors can protect water quality. Analyzing the width of corridors within an urban landscape can identify high- and low-quality corridors and guide corridor expansion and protection projects.
Types of Data Used in This Analysis:
- Protected Areas
- Parcel Data
Compiling and comparing existing city priority corridors can identify alignment and synergies between connectivity strategies across sectors. City agencies overseeing transportation, parks, public works, or other infrastructure and land management may have already developed corridor plans and projects, including greenways, bikeways, or other sustainable transportation corriodors. Identifying priority corridors can help align habitat creation and connecton with other citywide goals for susatinability, bikeability, public health, park accessibility, and infrastructure, and broaden access to potential funding.
Types of Data Used in This Analysis:
- City Planning Data
Urban landscapes may include many existing linear open spaces that can be converted to connections between habitats and patches. Calculating the abundance, size and location of features, such as transportation corridors (greenways, walkways, railroads), utility corridors (powerlines), and creeks or rivers, can be an important first step towards creating new or improved corridors. Such connections are critical for facilitating movement of both humans and wildlife across the city.
Types of Data Used in This Analysis:
- Roads and Infrastructure
- Waterways
Many plants and animals are unable to cross even narrow gaps in canopy or green cover. Identifying gaps in otherwise continuous linear open spaces can highlight important opportunities to enhance habitat connectivity. Filling these small gaps with native vegetation or new trees can generate significant benefits for biodiversity.
Types of Data Used in This Analysis:
- Land Cover / Land Use
- Canopy Data
- Waterways
Matrix Quality
Summarizing the proportion of a city’s total area covered by tree canopy provides a snapshot of the extent of the urban forest and can be a baseline for canopy cover targets and policies. Calculating canopy cover at the neighborhood or city block scale may reveal spatial disparities in canopy cover distribution across urban areas. Tree canopy cover has been linked with substantial benefits for biodiversity, urban heat, surface runoff, carbon sequestration, and public health.
Types of Data Used in This Analysis:
- Canopy Cover
- Land Cover / Land Use
Softscape includes ground-level and on-structure vegetation or water. Pervious softscape plays an important role in absorbing stormwater and urban heat, while also providing benefits for human health and habitat for plants and animals. Understanding how softscape is distributed in the urban landscape can be helpful for identifying plantable areas or, conversely, “hotspots” of low softscape where converting impervious cover to softscape or creating on-structure greening may be important strategies.
Types of Data Used in This Analysis:
- Land Cover / Land Use
The green area ratio is a quality- and area-weighted score for green space within a specified urban area. It is calculated by 1) multiplying the total area of each type of greening by the weighted value for that type, 2) summing across all greening types, and then 3) dividing by the total site surface area. Three greening types are commonly specified as part of this score. Ground-level green spaces receive a full score of 1, since they are generally more accessible to plants and animals, providing greater benefits to overall biodiveristy. Green roofs are worth 0.7, and exterior vegetated walls recieve 0.5. A green area ratio score can be useful for estimating the quantity and quality of a city’s green areas and tracking change over time.
Types of Data Used in This Analysis:
- Protected Areas
- Land Cover / Land Use
Road density highlights regions within the urban matrix that are more or less fragmented by roads. It can be particularly useful to weigh the road density measurements by traffic speed to better approximate the permeability of the landscape to wildlife. Areas with denser and faster road networks fragment the landscape and create barriers to wildlife movement. Planners can layer the resulting map of road density with other analyses to identify key areas for improving matrix quality. For example, roads immediately adjacent to large, high-quality patches are likely to reduce the value of the patch to wildlife.
Types of Data Used in This Analysis:
- Roads and Infrastructure (Roads and infrastructure data are typically available at local, regional, and national scales)
Habitat Diversity
Quantifying habitat diversity defines, maps, and summarizes the number of distinct habitats currently present in an urban area. Different habitats will support unique suites of species. Plantings and green spaces that contain a diversity of native habitats in suitable locations will be more likely to support a greater diversity of plant and animal species.
Types of Data Used in This Analysis:
- Habitat Survey
- Street Tree Inventory
Vertical complexity is an important characteristic that distinguishes distinct habitats and supports landscape heterogeneity and biodiversity. Native ecosystems tend to contain a diversity of plant communities with varying vertical structure, ranging from habitats with several layers of vegetation including an overstory canopy, a tall shrub layer, and an understory to having just one structural layer, such as just groundcover or canopy cover. Summarizing land cover data or maps of vegetative communities can reveal areas with little vertical structure and highlight opportunities for understory planting, tree planting, or another strategy to enhance the vertical complexity in existing green spaces.
Types of Data Used in This Analysis:
- Land Cover / Land Use
- Street Tree Inventory
Habitat Zones are distinct regions of the city that are best suited for certain habitat types. They are delineated based on a combination of historical habitat distribution, contemporary ecological conditions, and other biophysical constraints, such as geology, hydrology, and climate. Designating habitat zones is a powerful tool to guide site-level design that aligns with landscape-scale goals to support coherent urban ecosystems.
Types of Data Used in This Analysis:
- Habitat Survey
- Soil Maps
- Satellite Imagery
- Digital Elevation Model
Notes: Habitat surveys are typically conducted at local scales, resulting in maps of distinct ecological communities. These datasets can be created by city staff, consultants, or partnerships with local academic institutions.
Native Vegetation
The percent of street trees that are native is an important measure of the urban forest’s support for native wildlife. Native tree species often support a wide range of native mammals, birds and insects with which they have evoloved over thousands of years. Native trees may also be better adapted to local climate and soils, making them potentially more resilient selections for street tree plantings. Identifying streets with a low percentage of native trees can guide future tree planting efforts.
Types of Data Used in This Analysis:
- Street Tree Inventory
The amount of landscape area composed of native species can be expressed in terms of percent cover. This analysis is more feasible to conduct on a small scale, such as for a single park, green space, or landscaped area. Native plants have long histories of co-evolution with native wildlife, so greater amounts of native vegetation better supports native wildlife species by providing high-quality resources.
Types of Data Used in This Analysis:
- Street Tree Inventory
- Land Cover / Land Use
This analysis—not nessecarily spatial—calculates the porpotion of native species in a given plant palette. Native vegetation better supports native wildlife species by providing high-quality resources due to long histories of co-evolution.
Types of Data Used in This Analysis:
- Street Tree Inventory
Special Resources
Prominent trees may be large and old, native, a species that is threatened or rare, or have especial cultural or historical significance to the local community. These trees may have disproportionate benefits for urban cooling and interception of stormwater, and often have an outsize role in supporting biodiversity through supply of food (e.g. oaks), shelter, and vertical structure. Prominent tree status can be linked to additional protections and management recommendations.
Types of Data Used in This Analysis:
- Street Tree Inventory
Water in urban systems will often follow historical creek beds, pond and wetland locations – regardless of whether these features are still present. Understanding and mapping the location of historical water flow can shed light on modern urban flooding patterns, and guide practices such as stream daylighting and other restoration acitivities.
Types of Data Used in This Analysis:
- Waterbodies and Wetlands
- Historical Waterbodies and Waterways
Wetlands and open water are key special resources that support a diversity array of plants and animals. These features are also particularly sensitive to urban runoff and pollution. Comprehensively mapping the distribution of wetlands and open water in urban areas using satellite imagery or existing data sources is an important first step in guiding management and protection of urban aquatic species.
Types of Data Used in This Analysis:
- Waterbodies and Wetlands
- Waterways
Wetland buffers are zones of (often) vegetated land that surrounds wetland, marsh, or bog habitats. Wetland soils, plants and wildlife can be particularly sensitive to water pollution and urban runoff. Vegetated buffers can help mitigate water quality impacts from urban runoff, damper noise from urban spaces, and otherwise enhance habitat quality in existing wetlands.
Types of Data Used in This Analysis:
- Waterbodies and Wetlands
Management
Land ownership often dictates management and policy strategies for enhancing urban ecology. Up-to-date land ownership data can be used to generate statistics about urban ownership — such as the proportion of private vs public lands or commercial vs residential lands. These figures can guide targeted management or policy strategies that are compatible with land ownership in priority areas.
Types of Data Used in This Analysis:
- Parcel Data
Areas of short grasses which are frequently mowed have low ecological value, but may present opprtunities for habitat creation through native plantings, tree plantings, and other restoration. Mapping areas of managed grasses can be a first step towards identfying opportunity areas for planting efforts, or can help guide targets for new policies and programs such as turf replacement programs.
Sensitive habitats include areas that are particularly vulnerable to water pollution, air pollution, pesticides, or recreational use. The Habitat Zones analysis (see previous analysis under habitat diversity) can be a foundation for this analysis, or sensitive habitats can be designated by proximity to key features such as creeks, ponds, or wetlands. Sensitive habitat areas can benefit from special guidelines and policies such as limited recreational access or prohibited pesticide use.